Download Objectives, 9/18/08: Mitosis

Objectives, 9/18/08: Mitosis
1.  Apply appropriate terminology to describe
genetic characteristics of cells.
2.  Model and explain how genetic information
is transferred from one generation of cells
to the next through the process of mitosis.
- Use a diploid cell that is heterozygous for two
genes located on separate chromosomes
(unlinked).
G1: Cell’s DNA is
unduplicated
t
T
f
F
G2: DNA is duplicated
T
t
T
t
f
F
F
f
Metaphase
- duplicated chromosomes line up at equatorial
plane (centromeres align)
t
t
f
f
T
T
F
F
Metaphase  Anaphase
- sister chromatids separate at centromere
- chromatids move into daughter cells
t
t
f
f
T
T
F
F
Products: 2 cells formed
t
t
T
F
f
T
f
F
Use the information in the table above to answer questions
about Rascal. Rascal is a large, black dog with a pointy
nose and droop-down ears.
Important notes:
- Rascal’s mother is small and yellow and has a flat nose.
- Ear and nose shape are linked, meaning they occur at
different loci on the same chromosome (see above for
example of linked genes). Genes for size and color occur on
separate chromosomes. (Hint: you will draw 3 homologous
pairs.)
1.  What is Rascal’s genotype?
2.  Cell at G1
3.  Cell at G2
4.  Cell at metaphase of mitosis
5.  Cell products of mitosis
1. What is Rascal’s genotype?
Rascal is a:
large
black dog with a
pointy nose and
droop-down ears.
Important notes:
- Rascal’s mother is small and yellow and has a flat nose.
Phenotype Dominant Alleles Recessive Alleles Nose Shape Pointy (N) Flat (n) Ear Shape Upright (E) Down (e) Fur Color Black (B) Brown (b), Yellow (b’), White (b’’) Size Large (L) Small (l), Medium (l’) *Nose shape and Ear shape are linked on the same chromosome
KEY
Rascal is a large, black dog with a pointy nose and droop-down ears.
Important notes:
- Rascal’s mother is small and yellow and has a flat nose.
1.  What is Rascal’s genotype?
Phenotype Genotype Rascal’s genotype is: L l B b’ N n e e
large L l black B b’ pointy nose N n droop‐down ears e e In order to express the phenotype of droop-down ears, Rascal must have only
recessive alleles of the ear shape gene. Rascal is homozygous recessive for ear
shape.
All of Rascal’s other genotypes must be heterozygous. We know this because the
phenotypes of large, black, and pointy nose are associated with dominant alleles,
therefore Rascal must have at least one dominant allele for each. However, we
are also given information about Rascal’s mom – she has only recessive traits, so
can only pass on recessive alleles to her offspring. Rascal must have inherited
dominant alleles from his father.
KEY
2. Cell at G1
e
b’
N
L
B
e
n
l
KEY
3. Cell at G2
e
e
N
N
e
n
b’
b’
L
L
B
e
n
l
l
B
KEY
4. Cell at
Metaphase of
Mitosis
KEY
5. Products
of mitosis